Add ability to import/export tagging rules

- Add missing translations
- Add some tests
- Add `/api/taggingrule/export` API endpoint
- Add baggy theme
- Add error message when importing tagging rules failed
- Also fix all translations (I think we are good now)

src/Wallabag/CoreBundle/Form/Type/TaggingRuleImportType.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace Wallabag\CoreBundle\Form\Type;
+
+use Symfony\Component\Form\AbstractType;
+use Symfony\Component\Form\Extension\Core\Type\FileType;
+use Symfony\Component\Form\Extension\Core\Type\SubmitType;
+use Symfony\Component\Form\FormBuilderInterface;
+
+class TaggingRuleImportType extends AbstractType
+{
+    public function buildForm(FormBuilderInterface $builder, array $options)
+    {
+        $builder
+            ->add('file', FileType::class, [
+                'label' => 'config.form_rules.file_label',
+                'required' => true,
+            ])
+            ->add('import', SubmitType::class, [
+                'label' => 'config.form_rules.import_submit',
+            ])
+        ;
+    }
+
+    public function getBlockPrefix()
+    {
+        return 'upload_tagging_rule_file';
+    }
+}